The invention relates to a rollover protection system, comprising
a roll bar body which in a rollover accident is supported on a structural part of the motor vehicle and the end face of which is provided with at least one supporting element over which the motor vehicle rolls in a rollover accident, and
a predetermined deformation point for reducing peak loads in a rollover accident.
Such rollover protection systems serve to protect the occupants of motor vehicles without a protective root, typically convertibles or sports cars.
It is known in the art to provide a permanently installed roll bar spanning the entire width of the vehicle.
This solution has the drawback that it increases air resistance and driving noise, quite apart from detracting from the appearance of the vehicle.
It is also known in the art to assign each vehicle occupant a permanently installed roll bar, the height of which is not adjustable. This solution is typically used for sports cars to emphasize the car""s sporty appearance.
Widely known design solutions for convertibles comprise a roll bar which is normally retracted and which, in case of danger, i.e. in case of an impending rollover, is quickly deployed into a protective position to prevent the vehicle occupants from being crushed by the rolling vehicle.
These solutions typically comprise a roll bar body that is U-shaped or is formed by a structural section and is guided in a guide element that is permanently fixed to the vehicle. The guide element is fixed inside a cassette housing. This roll bar body is normally kept in a lower initial position by a holding device against the bias of a compression spring drive mechanism. In the event of a rollover it is deployed to its upper protective position through the spring force of the compression spring drive mechanism, controlled by a sensor, which releases the holding device. An actively engaging locking device, i.e. a retraction blocking mechanism, then prevents the roll bar from being pushed in.
Each vehicle occupant is assigned one cassette.
The holding device typically comprises a holding element that is fixed to the roll bar body and is mechanically linked with a release mechanism on a sensor-controlled tripping system. This tripping system normally comprises a release magnet, a so-called crash magnet, or a pyrotechnically activated release device.
The locking device that serves as a retraction blocking mechanism typically comprises a pivotably coupled, spring-biased locking pawl with tooth segments and a fixed toothed bar, a locking pin or the like. One locking element is connected with the roll bar while the other is fixed to the vehicle.
Such a cassette construction of a rollover protection system with a U-shaped roll bar is disclosed, for instance, in German Laid Open Publication DE 43 42 400 A1. An alternative cassette construction with a roll bar body in the form of a structural section is disclosed particularly in German Patent Specifications DE 195 23 790 C1 and DE 198 38 989 C1.
The aforementioned known rollover protection system as described in German Laid Open Publication DE 43 42 400 A1 comprises a housing in the form of a U-shaped cassette that is open on one side and has two sidewalls, which on the open side of the cassette each have an outwardly bent angular section for mounting the cassette to the vehicle. A bottom plate is furthermore mounted to the sidewalls, which are interconnected at their end face by a cover wall. The rollover protection system further has a U-shaped roll bar comprising a curved section and two parallel tubular legs, each of which has a closed lateral surface and the open ends of which are interconnected by means of a stiffening cross-member-type connection element.
The system further comprises two standpipes, one end of which is fixed to the housing floor and the interior of which receives a compression spring that acts as the sole drive of the roll bar. These standpipes are each axially enclosed by a tubular leg and also have a closed lateral surface. They are further provided with a guide block, which is mounted to the upper end of the housing, flat against the sidewalls of the cassette, and which has guide openings for additional outer guidance of the tubular legs.
The alternative rollover protection system of the prior art according to the above-cited German Patent Specification DE 198 38 989 C1 has a roll bar body configured as a box-type section that is reinforced against bending and extends over the entire width of the bar. It is guided in a box-type basic section, i.e. the guide section, which is fixed to the vehicle and forms the cassette. The end face of the bar body is provided with a positive-locking cross-member-type supporting element. In a rollover accident, the vehicle rolls over this support element, i.e. this element is in direct contact with the ground. In the case of the similarly supported above-cited German Patent Specification DE 195 23 790 C1, the roll bar is made of a spectacle-shaped bar section, which is guided in a guide section that is fixed to the vehicle and extends only over a partial area of the bar section. In both designs, a toothed bar screwed to each bar section and a toothed pawl pivotably coupled to the guide section are provided as locking devices.
In a rollover accident, the rollover protection system must absorb the abruptly occurring impact load, particularly in the moving direction of the roll bar body, through the roll bar body and, in the case of deployable systems, also through the guide element and its fixation in the vehicle as well as the locking device and its fixation (retraction blocking mechanism). According to the latest findings, particularly in rigid systems, the forces that occur, can reach short-term peak loads of more than 10 tons depending on the speed and weight of the vehicle as well as the impact angle and the nature of the impact surface. The basic load that typically occurs and for which the systems are designed is approximately 5.0-7.0 tons.
To be able to absorb these high forces, the strategy has thus far been to design the entire deployable rollover protection system as a reinforced, rigid, i.e. non-deformable system. The roll bar body, the guide element and its fixation on the vehicle were designed as a non-deformable rigid system up to the highest possible loads. Furthermore, the retraction blocking mechanism, i.e. the locking components and their fixation means, i.e. the dimensioning of the toothed racks and their mounting screws or, concretely, their positive locking seat within the roll bar body as well as the locking pawl and the bolts by means of which it is coupled to the guide element, including the bolt bearing in the guide element, were designed for very high loads.
This strategy, however,
proved to be economically inefficient because of the excessively high cost of materials,
would require a correspondingly larger overall volume for the reinforced elements, which is not usually available, so that there are limits to the load absorption, and
harbors the inherent risk that the elements of the retraction blocking mechanism may be abruptly destroyed, so that the retraction blocking mechanism would consequently lose its protective function completely.
If on the other hand the roll bar body/guide element system is made less rigid, it can be deformed when higher forces occur. Since this deformation is uncontrolled, the roll bar body may be deformed in such a way that it will partially lose its protective function.
German Laid Open Publication DE 199 31 224 A1 further discloses a rollover protection system in which the U-shaped roll bar is made of a brittle material, typically a fiber-reinforced plastic. Each leg is connected with the vehicle chassis by a deformation element. This system deliberately intends to increase the rigidity of the rollover body by means of the brittle material. The deformation element is intended to prevent the rollover body from abruptly fracturing if certain load limits are exceeded. This known measure, however, is limited to roll bars that are made of a special non-metallic material. Furthermore, it cannot be used for deployable systems, only for rigid systems.
German Publication DE 44 44 894 furthermore describes a roll bar whose curved support zones are equipped with energy absorbing enclosure parts. This serves to protect the vehicle occupants against impact to the head. Accordingly, these deformation elements are designed only for the type of loads that are normally assumed for enclosure parts in the interior of the vehicle. High peak loads as described above cannot be absorbed.
The object of the invention is to design a rollover protection system based on the principle of a predetermined deformation point in such a way that it can be used in both rigid and especially also in deployable systems as well as in systems that are equipped with typical metal roll bar bodies.
According to the invention, this object is attained by a rollover protection system for motor vehicles comprising
a roll bar body which in a rollover accident is supported on a structural part of the motor vehicle and which at its end face is provided with at least one support element over which the vehicle rolls in a rollover accident, and
a predetermined deformation point for reducing peak loads in a rollover accident,
characterized in that the support element is configured as a predetermined deformation point for a limited, defined deformation path in load direction according to a given force/path diagram for energy degradation.
In deployable protection systems, this object according to the invention is attained by a rollover protection system for motor vehicles comprising
a roll bar body that is guided in a guide element fixed to the vehicle and is normally held by a holding device in a lower, retracted initial position against the force of at least one compression spring-loaded drive mechanism, and when the holding device is released, the roll bar body is deployed by the spring force of the compression spring drive mechanism and is locked in an upper protective position by a retraction blocking mechanism, and its end face is provided with a cross-member-like support element over which the vehicle rolls in case of a rollover accident,
characterized in that the roll bar body, the associated guide element and its fixation on the vehicle, as well as the retraction blocking mechanism are configured as a rigid system relative to the maximum load occurring in a rollover accident, and the cross-member-like support element is configured as a predetermined deformation point for a limited, defined deformation path in moving direction of the roll bar body according to a given force/path diagram for energy degradation.
This intrinsically rigid roll bar system prevents uncontrolled deformation of the system and thus a total loss of function. Providing the inventive predetermined deformation point in the cross-member-like support element makes it possible effectively to reduce the peak forces occurring in the support element in a rollover accident through the deformation energy at the very beginning of the impact, that is to say at the instant when the cross-member-like support element contacts the ground. The maximum load can thus be reduced by simple means and without increasing the overall volume required for the roll bar system components that are provided for the vehicle structure in the flow of forces, i.e. the roll bar body and, in deployable systems, its guide element and the retraction blocking mechanism. This makes it possible, in particular, to prevent shearing of the tooth flanks of the locking device that forms the retraction blocking mechanism, or even shearing of the components of its fastening elements.
Since deformation can occur only via a limited path in moving direction, the protective function of the retraction blocking mechanism is preserved in every case.
A further advantage of the solution according to the invention is its ready applicability to existing rollover protection systems, since the xe2x80x9cdeformation cross memberxe2x80x9d can be integrated in existing systems largely without affecting the overall volume and weight.
The invention can furthermore be applied to a wide variety of roll bar designs, particularly U-shaped metal roll bars or roll bars made of extruded sections, without any limitation regarding the aesthetic design.
Embodiments of the invention are identified in the dependent claims and will become clear also from the description of the figures.